Vane type thermal switch



June 9, 1953 P. SITZER 2,641,666

VANE TYPE THERMAL swn'cn Original Filed July 26, 1943 INVENTOR ffi/z /P 5/ T25? ATTORNEYfi Patented June 9 1953 UNITED VANE TYPE THERMAL SWITCH Philip Sitzer, Irvington, N. -J., assignor to Tung- Sol Electric Inc., a corporation of Delaware Continuation of application Serial No. 496,187,

July 26, 1943.

1949, Serial No. 70,285

4 Claims. (01. 200-113) This invention relates to thermally operated switches and more particularly to snap action switches of the vane type.

One object of the invention is to provide a new and improved switch of the above character having a more precise, rapid contact action.

Another object of the invention is a new and improved thermally operated switch having substantially uniform operating characteristics over extended periods of time.

Another object of the invention is a new and improved thermal switch wherein improved contact life is obtained.

Still another object is a thermal switch having motion amplifying means coupling the contacts with the contact operating means.

The above and other objects will become more apparent from the following description and accompanying drawings.

In the drawings- Fig. 1 illustrates a vane type unit embodying the invention;

Fig. 2 is a view at right angles to Fig. 1 of the switch mechanism per se;

Fig. 3 is a view similar to Fig. 2 disposed at 180 thereto;

Fig. 4 is a view similar to Fig. 1 showing the control circuit open;

Fig. 5 is a sectional view along the line 5-5 of Fig. l;

' Fig. 6 is a circuit diagram in which the switch is employed;

Fig. '7 is a view similar to Figs. 1 and 4 showing a modification of the invention;

Fig. 8 is a view on the line 88 of Fig. 7; and

Fig. 9 is a back view of certain of the parts.

The thermal or current responsive switch according to the invention embodies among other features a snap-acting vane which through suitable actuating means is caused to respond to temperature changes and move from one of its positions to the other. A spring arm, which is fixed at one end and carries one of a pair of cooperating contacts on its other end is coupled intermediate its ends to the actuating vane so that the linear travel of the actuating vane tends to result in a substantially larger linear travel of the movable contact. The travel of the contact is limited, however, by the other of the pair of contacts which is positioned in the line of travel of the movable contact. Thus movement of the spring by the vane when the vane is actuated to contact closing position results in firm and positive contact pressure. Moreover, the spring mounted movable contact is provided with a This application January 11,

curved contacting surface so that in the closing operation a wiping action of the contacts is obtained which combined with the rapid amplified contact action greatly increases the life of the contacts. I have also found that the switch in accordance with the invention is extremely stable and dependable over long periods of operation, maintaining relatively uniform operating characteristics and being substantially unaffected by vibration. V

Referring to Figs. 1 to 5 of the drawings, I have illustrated the invention as embodied in a switch mechanism having a conventional casing or shell I, as for example, of cylindrical form but any suitable casing may be employed, or if desired no casing atall need be used. The shell I isclosed at the top and is carried at the bottom by an annular ring 2 of channel form, the shell I being provided with a flange I disposed underneath the upper flange of the annular ring 2. For convenience in illustration boththe casing and the switch mechanism embodying the invention are illustrated on an enlarged scale.

The switch mechanism comprises a frame of conventional shape having an insulating disc 3 carried by the annular ring 2 and an elongated bracket member 4 formed of any suitable metal and having a base part 5 turned at right angles from the frame member and secured fiat against the insulating disc 3 in any suitable manner, as for example, by the turned-over lugs 6 projecting from the terminal 1 up through openings in the insulating disc 3. The bracket 4 is formed some-; what in the shape of a U having an upper leg II and a lower leg I I and a buckling vane member I2 is rigidly fastened flat against the sides of these legs l0 and II and bridges the gap between these legs. This vane is proportioned with respect to the distance between the legs I!) and II so as to have a buckled or bowed shape depending upon the postion of the control. In the particular embodiment of the invention illustrated the vane I2 is formed of a gradually narrowing width from either end towards the midde thereof to have a narrow part I2 with the width gradually increasing in both directions therefrom to the legs I0 and I I of the bracket.

The vane I2 is controlled by an expansible and contraotible wire I3 and in the particular embodiment shown this wire is of double or loop form having its ends fastened to anchors I 4 and I5 projecting out from the lower part of the bracket 4. The wire is looped about an anchor I6 which is of L-shape with one of its legs fastened rigidly to the upper part of the vane I2 and an insulat 3 ing sleeve or ring I! is carried by this anchor l6 about which sleeve the wire I3 passes and is looped. The anchor 16 is fastened to the vane I2 at a point immediately below the leg ID of the bracket so that when the wire 13 expands and 4 means may, however, be formed of a single spring with the part 26' being suitably fastened to a I point on the contact carrying member at a point contracts the upper part of the vane has applied thereto varying degrees of constraint, Fig. 1 illustrating the comparatively cold condition of the wire. The latter through the anchor 16 holds the vane l 2 in the substantially S position shown whereas in the position shown in Fig. 4 the wire [3 has been heated and caused to expand, thereby permitting the vane l2 to assume the substantially bowed position shown or other desired shape. The tension of the wire 13 may be adjusted in any suitable manner as for example by bending the anchors l4 and 15, or by rotating one of them in its socket. The anchor I5 is insulated from the frame in any suitable manner for example, by the insulating sleeve l5 illustrated.

The temperature and therefore the length of the expansion wire 13 :is governed 'by electrical heating means and in the particular example shown the wire is heated directly by current flownig therethrough. The .current .flows through the terminals 1 and 8 "from any suitable source of power and if desired a resistance 18 may beinserted in this 'he'atingcircuit.

The circuit to be controlled comprises a stationary contact 20 and a movable contact 2!. The stationary contact 20 is carried by a wire or arm 22 which is mounted on an insulating sleeve 23 carried by a bracket '24 which in turn is fast- (mad as indicated to the bracket 4. The free end of this smaller bracket :24 is bent around the insulator 23 which carries the wire 22. A jumper wire 25 connects the wire .22 with the terminal 9. The movable contact 2:! is supported independently of the vane 12 but is actuated by the buckling part thereof to control its opening and closing movements. This mounting comprises a spring arm 2:5" which directly carries the contact 2| and which in turn is fastened to and carried by a spring arm '25. The latter is attached at its lower end'to the leg H of theframe member '4 on the side of the leg 1 1| opposite to that to which the vane is attached. Both the spring member .2 5 and '26 are flat leaf-like springs, the spring 125" being much narrower than the spring 26 and being therefore weaker than the spring 26. The spring 216 is turned over at its upper end to form a substantially right-angled part 26" which extends over toward the vane '12. This spring 26, .26 is so arranged and attached to the bracket 1 that its ifree end or contact translating means 2 6" bears against the narrow part l2 :of the vane and this spring preferably bears against the vane in both theopenand closed positions of the contacts 20, 21, that is, this spring member 26 follows the buckling move-. ments of the vane l2 under the influence of its natural constraint, causing it to bear against the vane. The degree of pressure between the spring 26 and the vane I2 is greater when the contacts 20., 2| are closed than when they are opened by the movement of the part 12' of the vane away from the stationary contact.

The contact-carrying member 26 of the embodiment of Figs. 1 to 5' is preferably provided with a rounded edge 21 on the :partZ-B thereof so as to form an easy self-adjusting bearing engagement with the part l2 of the vane.

I have described the contact carrying :members :25" and 26 as being two separate spring members. The contact supporting or carrying between the contact and the point of attachment to the frame so that amplifying or motion multiplying action will be obtained.

The spring-bearing element 26' bears against the vane ['2 at approximately the same "point at which the movable contact 21 is carried in conventional practice and this bearing part 26' therefore moves through a distance corresponding to the movement of such movable contact in the old practice. Thus by following the buckling movements :of the -vane I2 the spring member 26 which is constrained to bear against the vane is snapped back and forth following the similar action of the vane l2 and this in turn snaps movable contact 2| into and out of engagement with the stationary contact 20.

Fig. 1 corresponds to the open circuit or low current (condition of the :expansible wire 13 which now is contracted and holds the snapping part l2 of the vane toward the right and .firmly holds the movable contact 2| in engagement with the contact 20. The position in Fig. 4, however, corresponds to the closed position of the circuit 7,, '8 or to the higher current position with the result that the wire 13 is expanded and permits the vane .12 to bring the vane part l2 toward the left with either the spring part 2% bearing more weakly against the vane or not touching it at all in whichposit-ion the spring at holds the contact 2! out of engagement with the contact 20. The vane 12 is so constructed and mounted that the movement of the part 12' is a snap .action movement in both directions, that is, as the wire is gradually contracts due to cooling, the upper part of the vane 12 is .gradually put under constraint by the wire l3 and the anchor 6 untilfinally the intermediate part [2' is caused to snap over to the right with a quick closing of the contacts 20 and 2|. The reverse action takes .place as'the wire li-l gradually expands :due to heating.

By the construction and arrangement shown andv described no current passes through the vane 12 or any part of it and accordingly the vane 12 may be accurately designed, constructed and mounted for accurate and 'eiiicient operation through a long life unaffected by the passage of current while the snap action of the part I2" of the vane which in conventional practice carries the movable contact is translated by the means shown to the movable contact 2|. The latter by being mounted on the spring arm 25" is caused to have .a slight wiping movement on the relatively stationary contact 20 upon closing and opening.

The at present preferred modification of the invention is illustrated in Figs. 7 and 8. Herethe contact 21 is directly mounted upon :a spring arm 25 similar to the spring arm 25"of"the above described modification so as to apply the wiping contact movement upon closing and open ing. This spring arm 25' is fastened to and carried on one of the surfaces :of the legs of an L- shaped member 30 and this member 30 is carried by the bracket frame 4. One leg 30' of the I member 38 extends toward and beyond the vane member 3!] is thus directly actuated by the snap action part i2 of the vane in both directions of movement it is not essential that the member 30 exert any appreciable pressure against the movements of the vane in either direction. This L member 30 is preferably of a slightly springy metal and is of sufficient body and strength to carry and support the movable contact 21 through the roughest usage to which the switch may be put. As indicated, it is desirable that this contact-carrying member exert only a very little pressure in either of the two positions which the vane is designed in the particular embodiment shown to occupy. In furtherance of this end this L member 30 is not directly mounted on the bracket frame 4 or the leg H of this frame but is fastened fiat against a narrower strip 32 of springy material which projects upwardly above the leg I I of the frame member to serve as a spring pivotal mounting for the wider and heavier member 39. In the particular embodiment shown, the outer end of the leg 39' of the L member 30 is continued by a layer of metal 33 which extends around the vane part l2 forming a slot 3!. This continuing strip 33 may be formed by extending the end of the leg 30 in the direction taken by the additional part 33 so that the use of the additional part 33 as an extra piece is eliminated or it may be a separate strip as shown. Preferably the vane part 12 has a loose fit in the slot 3| so as to have some slight play therein.

In this embodiment one leg of the L-shaped member 39, the spring 32 and the spring 25' may be made of a single member or may even be formed integrally with the horizontal or transverse le of the L-shaped member 30. The movabl contact is displaced from the line of thrust as determined by the transverse leg of member 30 and is displaced in a direction on the side opposite to the point of attachment of the contact carrying means to the frame. This provides rapid and positive contact movement and contributes materially to the greatly improved stability and uniformity of operation over extended periods of time as well as to increased contact life.

In the position of Fig. 7 where the contacts 20 and 21 are closed the vane engages the inner wall of the slot 3|. When the contact is open the vane engages the outer wall of the slot 3|. In this modification of the invention the vane is neither affected by current flowing through it or any part of it nor appreciably affected by the means shown for translating the snap action movements of the part l2 to the movable contact 2|. I have found that this enhances the accuracy and efficiency of the control mechanism and also substantially increases the life of the mechanism.

I have illustrated the wire I3 as being fastened to the anchor I6 by means of the loop of the wire passing thereabout but it is understood that a single wire having its end fastened to the anchor I6 or its equivalent could be used. The shape of the vane 12 in its different positions is roughly illustrated in the drawings but it is understood that the exact shape of the vane is difiicult to illustrate on small drawings.

The new and improved switch according to the invention embodying, among other features, a snap acting vane coupled to a movable contact through motion amplifying means and also em- 6 bodying a contact mounting insuring positive and firm contact with contact wiping action, possesses greatly improved stability, has materially increased the life, and provides substantially uniform operating characteristics over long periods of time.

This is a continuation of my application for United States Patent, Serial No. 496,187, filed July 26, 1943, and now abandoned entitled Vane Type Thermal Switch.

I claim:

1. A thermal switch comprising a frame, a fixed contact, a fiat spring fastened at one end to the frame and carrying a contact at the free end thereof positioned for engagement with said fixed contact when the spring is moved against the bias thereof, a buckling vane having its ends fastened against the frame in a constrained position to cause a portion thereof to snap from one position to another when operated, thermal responsive means for actuating the buckling vane, and means coupling said portion of the vane with said spring at a point between the ends thereof for imparting to the free end of said spring positive movement to close the contacts in response to movement of said portion of the buckling vane which is substantially greater than that of said vane portion and imparting a wiping movement to the spring carried contact upon engagement and disengagement with the fixed contact.

2. A thermal switch according to claim 1 wherein said coupling means loosely embraces the vane to provide positive contact movement in both directions of vane movement.

3. A thermal switch according to claim 1 wherein said coupling means loosely engages the snapping portion of the vane and is carried by said spring.

4. A vane type thermal switch mechanism comprising a buckling vane, thermally controlled means for causing a part of said vane to assume snap action movements, a movable contact-carrying member separate from said vane and means operatively connecting said contact-carrying member with said vane part for translating the snap action movements thereof to the contactcarrying member, said snap action movement translating means comprising a metal strip having a slot through which the vane loosely passes for directly actuating the contact-carrying member by the vane in both directions of movement and through a position of rest in movement from the open to the closed contact positions and vice versa.

PHILIP SITZER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,314,524 Kunkle Sept. 2, 1919 1,495,998 Gilchrist et al. June 3, 1924 1,622,721 Hook Mar. 29, 1927 2,040,405 Persons May 12, 1936 2,133,309 Schmidinger Oct. 18, 1938 2,256,499 Schmidinger Sept. 23, 1941 FOREIGN PATENTS Number Country Date 283,631 Great Britain Jan. 11, 1928 527,561 Germany June 19, 1931 

